From a9abc7831e45257d334cfa682746b6cadf9e95d9 Mon Sep 17 00:00:00 2001
From: Adam Cozzette <acozzette@google.com>
Date: Fri, 6 Jul 2018 14:12:33 -0700
Subject: Fix initialization with Visual Studio

It appears that Visual Studio does not work well with std::once_flag
because it has a bug causing it to initialize that during dynamic
initialization instead of constant initialization. This change works
around the problem by using function static initializers instead.

@gerben-s originally wrote this change for the Google-internal codebase
but I am just cherry-picking it here.

This fixes #4773.
---
 .../protobuf/generated_message_reflection.cc       | 26 +++++++++-------------
 1 file changed, 10 insertions(+), 16 deletions(-)

(limited to 'src/google/protobuf/generated_message_reflection.cc')

diff --git a/src/google/protobuf/generated_message_reflection.cc b/src/google/protobuf/generated_message_reflection.cc
index 247f772c..74ad00e7 100644
--- a/src/google/protobuf/generated_message_reflection.cc
+++ b/src/google/protobuf/generated_message_reflection.cc
@@ -2327,32 +2327,26 @@ class AssignDescriptorsHelper {
 // automatically delete the allocated reflection. MetadataOwner owns
 // all the allocated reflection instances.
 struct MetadataOwner {
+  ~MetadataOwner() {
+    for (auto range : metadata_arrays_) {
+      for (const Metadata* m = range.first; m < range.second; m++) {
+        delete m->reflection;
+      }
+    }
+  }
+
   void AddArray(const Metadata* begin, const Metadata* end) {
     MutexLock lock(&mu_);
     metadata_arrays_.push_back(std::make_pair(begin, end));
   }
 
   static MetadataOwner* Instance() {
-    static MetadataOwner* res = new MetadataOwner;
+    static MetadataOwner* res = OnShutdownDelete(new MetadataOwner);
     return res;
   }
 
  private:
-  // Use the constructor to register the shutdown code. Because c++ makes sure
-  // this called only once.
-  MetadataOwner() { OnShutdown(&DeleteMetadata); }
-  ~MetadataOwner() {
-    for (int i = 0; i < metadata_arrays_.size(); i++) {
-      for (const Metadata* m = metadata_arrays_[i].first;
-           m < metadata_arrays_[i].second; m++) {
-        delete m->reflection;
-      }
-    }
-  }
-
-  static void DeleteMetadata() {
-    delete Instance();
-  }
+  MetadataOwner() = default;  // private because singleton
 
   Mutex mu_;
   std::vector<std::pair<const Metadata*, const Metadata*> > metadata_arrays_;
-- 
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